U.S. patent number 5,587,446 [Application Number 08/456,540] was granted by the patent office on 1996-12-24 for hyperbranched polymers from ab monomers.
This patent grant is currently assigned to Cornell Research Foundation, Inc.. Invention is credited to Sadahito Aoshima, Jean M. J. Frechet.
United States Patent |
5,587,446 |
Frechet , et al. |
December 24, 1996 |
Hyperbranched polymers from AB monomers
Abstract
A process for preparing hyperbranched polymers from AB monomers
using a self constructing approach is disclosed. Hyperbranched
polymers of a living-like character produced by such process are
also disclosed.
Inventors: |
Frechet; Jean M. J. (Ithaca,
NY), Aoshima; Sadahito (Kashiwa, JP) |
Assignee: |
Cornell Research Foundation,
Inc. (Ithaca, NY)
|
Family
ID: |
23313912 |
Appl.
No.: |
08/456,540 |
Filed: |
June 1, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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335947 |
Nov 8, 1994 |
|
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Current U.S.
Class: |
526/333; 526/238;
526/292.9; 526/293; 526/320; 526/321; 526/332; 526/346;
526/347.1 |
Current CPC
Class: |
C08F
297/00 (20130101); C08G 83/005 (20130101) |
Current International
Class: |
C08F
297/00 (20060101); C08G 83/00 (20060101); C08F
016/12 (); C08F 004/14 () |
Field of
Search: |
;526/332,333,293,292.9,238 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Zitomer; Fred
Attorney, Agent or Firm: Jacobs; Bruce F.
Parent Case Text
This is a divisional of copending application Ser. No. 08/335,947
filed Nov. 08, 1994.
Claims
What is claimed is:
1. A hyperbranched polymer produced from an AB monomer in which A
and B are reactive groups that react independently of each other in
which group A is a polymerizable group and group B is a precursor
of a moiety B* which initiates the polymerization of A as a result
of being activated, wherein said hyperbranched polymer comprises an
AB*.sub.x macro-monomer in which x is an integer that increases as
polymerization increases, said hyperbranched polymers having a
living character in that said polymer has active sites A* and B*
which are reactable with A groups, AB monomers and
nucleophiles.
2. The polymer of claim 1, wherein the active sites A* and B* are
reactive with nucleophiles.
3. The polymer of claim 1, wherein the active sites A* and B* are
reactive with electrophiles.
4. The polymer of claim 1, wherein the polymer has functionalized
chain ends.
5. The polymer of claim 1, wherein the AB monomer is selected from
the group consisting of
1-(2-vinyloxyethyloxy)-1'-[2-(1-acetoxyethoxy)-ethyloxy]-4,4'-isopropylide
nediphenol;
1-vinyloxymethyl-4-(1-acetoxy)ethyloxymethylcyclohexane;
1-(2-vinyloxyethyl)-4-[(1-acetoxyethyloxy)ethyl]terephthalate;
2-(2-vinyloxyethyl)-2-[(1-acetoxyethyloxy)ethyl]diethyl malonate;
1-(2-vinyloxyethyl)-3-[(1-acetoxyethyloxy)ethyl]-5-(2-methacryloyloxyethyl
oxyethyl)-1,3,5-benzene tricarboxylate;
1-[(4-ethenyl)-phenoxymethyl]-4-[4-(1-chloroethyl)phenoxymethyl]benzene;
4-(2-(1-chloroethyloxy))ethyloxystyrene; 4-(1-bromoethyl)styrene;
4-(1-chloroethyl)styrene, chloromethylstyrene,
3-(1-bromoethyl)styrene, and 3-(1-chloroethyl)styrene.
6. The polymer of claim 1, wherein the polymer has a degree of
branching of from about 0.05-0.95.
7. The polymer of claim 1, wherein the polymer has a degree of
branching of more than about 0.2.
8. The polymer of claim 1, wherein the polymer has a degree of
branching of more than about 0.3.
Description
BACKGROUND OF THE INVENTION
Structurally, polymers are classified as either linear or branched
wherein the term "branched" generally means that the individual
molecular units of the branches are discrete from the polymer
backbone, yet may have the same chemical constitution as the
polymer backbone. Thus, regularly reacting side groups which are
inherent in the monomeric structure and are of different chemical
constitution than the polymer backbone are not considered as
"branches"; that is, for example, the methyl groups pendant on a
polydimethylsiloxane chain or a pendant aryl group in a polystyrene
are not considered to be branches of such polymers. All
descriptions of branching and backbone in the present application
are consistent with this meaning.
The simplest branched polymers are the comb branched polymers
wherein a linear backbone bears one or more essentially linear
pendant side chains. This simple form of branching, often called
comb branching, may be regular wherein the branches are distributed
in non-uniform or random fashion on the polymer backbone. An
example of regular comb branching is a comb branched polystyrene as
described by T. Altores et al. in J. Polymer Sci., Part A, Vol. 3
4131-4151 (1965) and an example of irregular comb branching is
illustrated by graft copolymers as described by Sorenson et al,
Preparative Methods of Polymer Chemistry, 2nd Ed., Interscience
Publishers, 213-214 (1968).
Another type of branching is exemplified by cross-linked or network
polymers wherein the polymer chains are connected through the use
of bifunctional compounds; e.g., polystyrene molecules bridged or
crosslinked with divinylbenzene. In this type of branching, many of
the individual branches are not linear in that each branch may
itself contain side chains pendant from a linear chain and it is
not possible to differentiate between the backbone and the
branches. More importantly, in network branching, each polymer
macromolecule (backbone) is cross-linked at two or more sites to
other polymer macromolecules. Also the chemical constitution of the
cross-linkages may vary from that of the polymer macromolecules. In
this cross-linked or network branched polymer, the various branches
or cross-linkages may be structurally similar (called regular
cross-linked) or they may be structurally dissimilar (called
irregularly cross-linked). An example of regular cross-linked
polymers is a ladder-type poly(phenylsisesquinone) [sic]
{poly-(phenylsilsesquioxane)}. Sogah et al, in the background of
U.S. Pat. No. 4,544,724, discusses some of these types of polymers
and gives a short review of the many publications and disclosures
regarding them. U.S. Pat. No. 4,435,548, discusses branched
polyamidoamines; U.S. Pat. Nos. 4,507,466, 4,558,120, 4,568,737,
4,587,329, 4,713,975, 4,871,779, and 4,631,337 discuss the
preparation and use of dense star polymers, and U.S. Pat. Nos.
4,737,550 and 4,857,599 discuss bridged and other modified dense
star polymers.
Other structural configurations of macromolecular materials that
have been disclosed include star/comb-branched polymers, such
disclosure being found in U.S. Pat. Nos. 4,599,400 and 4,690,985,
and rod-shaped dendrimer polymers are disclosed in U.S. Pat. No.
4,694,064.
Hutchins et al, in U.S. Pat. Nos. 4,847,328 and 4,851,477, deal
with hybrid acrylic-condensation star polymers and Joseph et al, in
U.S. Pat. Nos. 4,857,615, 4,857,618, and 4,906,691, with condensed
phase polymers having regularly, or irregularly, spaced polymeric
branches essentially on the order of a comb structure
macromolecules.
M. Gauthier et al, Macromolecules, 24, 4548-4553 (1991) discloses
uniform highly branched polymers produced by stepwise anionic
grafting. M. Suzuki et al, Macromolecules, 25, 7071-2 (1992)
describes palladium-catalyzed ring-opening polymerization of cyclic
carbamate to produce hyperbranched dendritic polyamines.
Macromolecules, 24, 1435-1438 (1991) discloses comb-burst dendrimer
topology derived from dendritic grafting. U.S. Pat. No. 5,041,516
discloses other dendritic macromolecules.
The various architectures of these macromolecules results in a
variety of end product uses. It is desirable to produce
macromolecules that are hyperbranched (containing 2 or more
generations of branching) so as to enable the production of highly
functional macromolecules. Increasing the functionality of a
macromolecule at a multiplicity of sites within the macromolecule
can make it a much more useful molecule.
Dendrimers and hyperbranched polymers have received much attention
recently due to their unusual structural features and properties.
In the early 1950's, Flory, J. Am. Chem. Soc., 74, 2718 (1952)
discussed the potential of AB.sub.2 monomers, in which A and B are
different reactive groups which react with each other to form a
chemical bond, for the formation of highly branched polymers.
However, the formation of high molecular weight hyperbranched
polymers from AB.sub.2 monomers containing one group of type A and
two of type B was not accomplished until 1988 when Kim et al.,
Polym. Prep., 29(2), 310 (1988) and U.S. Pat. No. 4,857,630
reported the preparation of hyperbranched polyphenylene.
Numerous other hyperbranched polymers have been reported since that
time by Hawker et al., J. Am. Chem. Soc., 113, 4583, (1991); Uhrich
et al, Macromolecules, 25, 4583 (1994); Turner et al,
Macromolecules, 27, 1611 (1994); and others. See also U.S. Pat.
Nos. 5,196,502; 5,225,522; and 5,214,122. All of these
hyperbranched polymers are obtained by polycondensation processes
involving AB.sub.2 monomers. In general, these hyperbranched
polymers have irregularly branched structures with high degrees of
branching between 0.2 and 0.8.
The degree of branching DB of an AB.sub.2 hyperbranched polymer has
been defined by the equation DB=(1-f) in which f is the mole
fraction of AB.sub.2 monomer units in which only one of the two B
groups has reacted with an A group.
In contrast to hyperbranched polymers, regular dendrimers are
regularly branched, macromolecules with a branch point at each
repeat unit. Unlike hyperbranched polymers that are obtained via a
polymerization reaction, most regular dendrimers are obtained by a
series of stepwise coupling and activation steps. Examples of
dendrimers include the polyamidoamide (PAMAM) Starburst.TM.
dendrimers of Tomalia et al, Polym. J., 17, 117 (1985) or the
convergent dendrimers of Hawker et al, J. Am. Chem. Soc., 112, 7638
(1990).
Recently, some highly branched polymers have been prepared in
multistep processes involving a graft on graft technique that leads
to a dramatic increase in molecular weight as a result of
successive stepwise grafting steps. Examples of such polymers are
the Combburst.TM. polymers of Tomalia et al., Macromolecules, 24,
1435 (1991); U.S. Pat. No. 4,694,064; and the "arborescent"
polymers of Gauthier et al., Macromolecules, 24, 4548 (1991) and
Macromolecular Symposia, 77, 43 (1994).
The preparation of hyperbranched polymers by a chain growth vinyl
polymerization has not been accomplished previously.
DISCLOSURE OF THE INVENTION
Accordingly, the present invention is directed to a process for
preparing highly branched or "hyperbranched" polymers by a
chain-growth polymerization process using AB monomers. An AB
monomer is one that contains two reactive groups A and B, which
react independently of each other within a molecule; reaction onto
A is not required to trigger the reaction of B. The A group is
preferably a polymerizable vinyl group that is able to react with
an active moiety such as an anion, a cation, or a conventional
initiating or propagating moiety of the type well known in the art
of vinyl polymerization such as those described in Principles of
Polymerization, 3rd Ed., by G. Odian (Wiley) or in Polymer
Synthesis 2nd Edition by P. Rempp and E. Merrill (H uthig &
Wepf) to produce a new activated group A* that is capable of
further reaction with any A-containing moiety present in the
polymerization mixture to give an A'-A* unit in which A' is an
inactive group derived from A that acts as a building block of the
final polymer.
The B group is preferably a reactive group that can be activated by
an activator such as one or more external activator molecules like
(i) alkyl aluminum halides, e.g. EtAlCl.sub.2 and Et.sub.1.5
AlCl.sub.1.5, (ii) SnCl.sub.4, (iii) SnCl.sub.4 combined with
Bu.sub.4 NCl, (iv) HI combined with I.sub.2, or (v) CH.sub.3
SO.sub.3 H combined with Bu.sub.4 NCl and SnCl.sub.4 or SnCl.sub.4
combined with 2,6-di-tert-butylpyridine. Other external activators
include Lewis acids, bases such as hydroxides, butyl lithium,
amines and carbanions, heat, light, or radiation, which activate to
produce an anion, cation, or conventional initiating or propagating
moiety well known in the art of vinyl polymerization such as those
described by Aoshima et al, J. Polymer Science, A, Polymer
Chemistry, 32, 1729 (1994) or in Ishihama et. al. Polymer Bulletin
24 201 (1990) or in Higashimura et. al. Macromolecules 26 744
(1993). Once activated, B becomes B*. Any B, group present in the
polymerization mixture may react with any A-containing moiety
present in the polymerization mixture to afford a B'-A. unit in
which B' is an inactive group derived from B that acts as a
building block of the final polymer.
This invention represents a new concept whereby hyperbranched
polymers are obtained not from an AB.sub.2 type monomer as
described in the prior art, but from an AB monomer. The process
comprises "self-constructing" polymers that contain throughout
their growth a single polymerizable group A and a multiplicity of
propagating species such as A* or B*, for example, a carbenium ion.
In effect, an AB monomer becomes an AB*.sub.x -type macromonomer in
which x increases as the polymerization proceeds.
In the process of the present invention, the "monomer" consists of
polymerizable initiator molecules (AB molecules) that are activated
by an external event to produce activated polymerizable initiator
molecules (AB* molecules). Not all AB molecules need to be
activated to A-B* since both A* and B* can add to any available A
group, and any B group that remains inactivated may become
activated later as a result of an exchange process. These molecules
grow by adding to any available polymerizable A group present in
the reaction mixture in a process that involves successive and
repeated couplings of growing polymer chains with A-containing
moieties, including the growing chains themselves, until the
concentration of A groups is so reduced that the chain
polymerization process no longer proceeds at an appreciable
rate.
According to one embodiment of the present invention, an A-A
monomer is added during the polymerization, commonly in the later
stages of polymerization, prior to its completion or quenching, to
couple pre-formed molecules of hyperbranched polymer to increase
the molecular weight of the final hyperbranched polymer. An A-A
monomer is added in an amount and at a time such that precipitation
of the polymer does not occur. Too much A-A may lead to undesirable
crosslinking. If used, a suitable amount of A-A monomer is about
0.1 to 10 mole % of total monomer. As the amount of A-A increases,
the reaction generally requires greater monitoring to terminate it
prior to crosslinking or insolubilization. Suitable A-A monomers
may be selected from any of divinyl ether,
1,1'-bis(2-vinyloxyethoxy)-4,4'-isopropylidene diphenol,
diethyleneglycol divinylether, butanediol divinyl ether,
cylohexanedimethanol divinylether, hexanediol divinyl ether,
cyclohexanediol divinyl ether, poly(THF) divinyl ether,
polyethyleneglycol divinyl ether, ethylene glycol divinyl ether,
triethyleneglycol divinyl ether, tetraethyleneglycol divinyl ether,
divinylbenzene, bis-(4-ethenylphenyl)methane,
bis-1,2-(4-ethenylphenyl)ethane, ethyleneglycol dimethacrylate,
bis-1,2-(4-ethenylphenoxy)ethane, or
bis-1,4-(4-ethenylphenoxy)butane. Particularly preferred A-A
monomers are di-vinyl ether and bis-ethenylbenzene.
The process of the present invention has a "living-like" character,
whereby side reactions such as chain transfer and elimination
producing a double bond, (i.e. another A group) are substantially
eliminated. If such side reactions are not substantially eliminated
the polymerization would result in a crosslinked polymer, which is
highly branched but not soluble. Such a polymer would be quite
different from those of the present invention which retain their
living-like character and solubility. The ultimate end uses of the
polymers of the invention are also different from those of the
highly crosslinked insoluble polymers that would result if side
reactions were not substantially eliminated.
Because growing chains combine with each other, their number
decreases as the polymerization proceeds. However, the total number
of propagating species remains very high and essentially constant
because each growing polymer chain sees the number of its
propagating ends multiply as the polymerization proceeds while the
total number of individual chains decreases.
The "self-constructing" polymerization will generally not provide a
degree of branching of 1.0, because of thermodynamic, kinetic, and
steric factors that may prevent some sites from reacting in regular
fashion. Therefore, a hyperbranched polymer with a degree of
branching below 1.0, generally about 0.05-0.95, preferably above
about 0.2, more preferably above about 0.3, and still more
preferably above about 0.5, will result in all but ideal
conditions, i.e. when there are absolutely no side reactions and
growth follows a regular geometric pattern not affected by any
steric or similar factor. The degree of branching of an AB
hyperbranched polymer is the mole fraction of monomer units at
branch points or chain ends.
The hyperbranched polymers of the present invention retain their
living-like character in that the final polymer still contains many
active sites A* and B* that could be polymerized further by
addition of more A or AB monomer to produce larger hyperbranched
structures or star-like polymers with hyperbranched cores.
Moreover, the active sites A* and B* may be quenched to produce
many functionalized chain-ends. For cationic polymerizations,
suitable quenching agents are generally nucleophiles such as
methanol, amines, halides, water, the sodium salt of diethyl
malonate, or substituted phenyl lithium. In the case of anionic
polymerizations, suitable quenching agents are generally
electrophiles such as aldehydes, ketones, substituted alkyl or
benzyl halides, alcohols, or water. As a result, the hyperbranched
polymers have and can be designed for numerous end uses, many of
which are not possible for other polymers.
The hyperbranched polymers are useful in the formulation of
adhesives, carriers for drugs or biological materials, slow release
formulations, crosslinking agents, paints, rheology modifiers,
additives for coatings and plastics, inks, lubricants, foams,
components of cosmetic formulations, hairspray, deodorents and the
like, components of separation media, porosity control agents,
complexing and chelating agents, carriers for chiral resolution
agents, components of medical imaging systems, carriers for gene
transfection, and resist or imaging materials.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An example of the process of the present invention whereby a
hyperbranched polymer is prepared from AB monomer 1 is described in
Reaction Scheme 1: ##STR1## wherein R is ##STR2##
The A group of monomer 1 is a vinyloxy group that is known to
polymerize under cationic conditions. The B group is an
.alpha.-acetoxy alkyl ether that may be activated by addition of a
Lewis acid such as ethyl aluminum sesquichloride (C.sub.2
H.sub.5).sub.1.5 AlCl.sub.1.5 to afford AB* "living" moieties that
can initiate their own self-polymerization.
As is well known in the art, the living-like polymerization of
vinyl ethers requires that special conditions be maintained to
ensure that undesirable side-reactions such as crosslinking, chain
transfer or termination are avoided. The use of standard
precautions, such as those described for example in the review by
Sawamoto, Prog. Polym. Sci., 16, 111-172 (1991), are preferred. For
example, polymerization is generally carried out in the absence of
water and in the presence of agents such as ethers or heterocyclic
compounds that help stabilize the "living-like" chain ends
(propagating groups). Conditions must also be maintained to prevent
elimination reactions. Suitable conditions are well known in the
art and include the absence of water, selection and strength of a
Lewis acid and the complex formed between the Lewis acid and the
carbocationic center, the addition of a "basic" or "nucleophilic"
additive such as tetrahydrofuran, dioxane, ethyl acetate, or
tetrabutyl ammonium chloride, to stabilize the carbocationic
propagating center, and the like. For an anionic process, suitable
conditions include the use of a dry solvent such as tetrahydrofuran
or cyclohexane and the absence of water or electrophilic impurities
such as alcohols, aldehydes, ketones, bencylic or aliphatic
halides. The use of additives such as glymes or cyclic ethers
including tetrahydrofuran or dioxane, or tetramethyl
ethylenediamine (TMEDA), or hexamethyl phosphoramide (HMPA) or
crown ethers and cryptants (molecule-like crown ethers that can
complex ionic species) that help stabilize the prepagating center
is also well known in the art. (See, for example, P. Rempp and E.
Merrill in "Polymer Synthesis" 2nd Edition, chapter 5, (Huthig
& Wepf).
To simplify the representation in Reaction Scheme 1, it is assumed
that all AB molecules are transformed into AB* molecules at the
start of the process. This is not a requirement because both A* and
B* can react with any molecule containing a reactive A group.
Once the polymerization is complete, the activated A* and B* sites
can be terminated by addition of a suitable reagent. In the case of
a cationic polymerization as shown in Reaction Scheme 1, this
reagent could be a nucleophile like methanol, water, halide ion,
amine, or the sodium salt of diethyl malonate, or a substituted
phenyl lithium. In the case of an anionic polymerization, the
reagent could be an electrophile such as an aldehyde, ketone,
substituted alkyl or benzyl halide, alcohol, or water.
In Reaction Scheme 1, the active chain-ends or propagating sites
(A* and B* groups) are shown by a "+" sign indicating their
cationic nature. The counterions represented by the letter "X" and
a "-" sign may be any suitable counterion such as Et.sub.1.5
AlCl.sub.1.5 (OAc), C.sub.2 H.sub.5 AlCl.sub.2 OAc, and
I.sub.3.sup.-.
Reaction Scheme 2 shows a cascade of branches resulting from the
cationic polymerization of monomer 1. ##STR3##
This representation is used to convey the hyperbranched nature of
the polymer and it also illustrates the involvement of both A* and
B* groups in growth of the hyperbranched polymer.
Reaction Scheme 3 shows the structure of the polymer of Reaction
Scheme 2 after termination by the addition of methanol as described
in greater detail in the Examples. Other reagents may also be used
to effect termination. ##STR4## In this fashion, a hyperbranched
polymer containing numerous reactive groups at its chain ends is
obtained.
AB molecules useful in the present invention are best represented
by the formula A-(S).sub.p -B in which A and B are as defined
above, S is a spacer group separating A from B, and p is an integer
of 0, 1, or 2. In the specific compositions shown below a bond is
shown on A and B to show the point of attachment of either to the
other or to S. The term AB monomer as used herein means A-(S).sub.p
-B In this formula, if p is 2, there may two of the same S groups
or two different S groups. When p is 0, S is not present. A spacer
group S changes the distance between branch points and may
contribute to the final polymer properties such as resistance to
oil, elongation, shape, rigidity, or the like, or it may be used to
introduce reactive pendant groups, e.g. acrylic groups, masked
amines, masked alcohols or protected carboxylic groups. Any such
pendant group must be inert to the polymerization reaction used to
prepare the hyperbranched polymer. While any A, B, and S groups may
be used, they must be compatible with each other. The compatibility
of A, B, and S groups is related to the reactivity of A, B, S, A*
and B*. Compatible groups are those for which the reactivity of
both A* and B* with an A group will be substantially similar such
that the polymerization may proceed through either A* or B*. The
compatibility of the S group with A and B relate to its inability
to react chemically with A, B, A* or B* moieties for example to
cause the formation of a new active propagating center through
processes such as addition, chain transfer, or elimination
reaction. Since certain A, B, and S groups may not be compatible
with each other, preferred such groups are specified below by
compatible groups.
The first AB monomer grouping is represented by the formula A.sup.1
(S.sup.1).sub.p B.sup.1, wherein A.sup.1 is selected from any of
##STR5## R.sup.1 is H or C.sub.1 -C.sub.4 alkyl, preferably H.
R.sup.2 is H or C.sub.1 -C.sub.4 alkyl, preferably H.
A suitable companion B.sup.1 group for A.sup.1 groups may be
represented by the general formula: ##STR6## R.sup.3 is selected
from any of C.sub.1 -C.sub.4 alkyl, di-phenyl, aryl such as phenyl
or naphthyl, optionally substituted with one or more substituent
such as halo,cyano, C.sub.1 -C.sub.4 alkyl, and C.sub.1 -C.sub.4
alkoxy. Preferably, R.sup.3 is C.sub.1 -C.sub.4 alkyl, most
preferably methyl. R.sup.4 is selected from any of H or C.sub.1
-C.sub.4 alkyl. More preferably R.sup.4 is H. X.sup.1 is O. "t" is
0 or 1. X.sup.2 is OR.sup.5, OCOR.sup.5, or halo preferably chloro.
R.sup.5 is C.sub.1 -C.sub.4 alkyl, haloalkyl, aryl, or aralkyl,
more preferably methyl.
A suitable S.sup.1 group which may be used with the above described
companion A.sup.1 and B.sup.1 groups may be selected from any of
C.sub.2 -C.sub.12 alkylene, substituted C.sub.2 -C.sub.12 alkylene
wherein the substituents are selected from any of C.sub.1 -C.sub.4
alkyl or aralkyl wherein the alkyl is C.sub.1 -C.sub.4 ; ##STR7##
wherein m and n are the same or different and are each integers
from 0 to about 18, Ar.sup.1 and Ar.sup.2 are the same or different
and are aryl selected from phenyl, naphthyl, biphenyl, optionally
substituted with one or more substituents selected from C.sub.1
-C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy, halo, or acetoxy; ##STR8##
wherein y=0 or 1, and X.sup.3 is selected from any of O, S,
SO.sub.2, CH.sub.2 or CO; ##STR9## wherein R.sup.5 is C.sub.1
-C.sub.4 alkyl or aryl; ##STR10## polystyrene, polyisobutylene,
polyester, polyether, polyolefin, polyetherketone, polycarbonate,
polysulfone; or ##STR11## wherein W is ##STR12##
More preferably, S.sup.1 is selected from any of ##STR13##
Alternatively, the A, B and S groups in an AB monomer may be
represented by the formula A.sup.2 (S.sup.1)B.sup.2 wherein A.sup.2
is selected from ##STR14## wherein R.sup.6 is H or C.sub.1 -C.sub.4
alkyl, preferably H; Ar.sup.3 is aryl or N-alkyl-3-carbazoyl
wherein the alkyl is C.sub.1 -C.sub.8, preferably phenyl;
(X.sup.4).sub.y is O or CH.sub.2, preferably, X.sup.4 is O attached
to a phenyl Ar.sup.3 at the para position; and y is 0 or 1; B.sup.2
is selected from ##STR15## wherein R.sup.7 is selected from any of
H, CH.sub.3, C.sub.1 -C.sub.8 alkyl or aryl, preferably H; R.sup.8
is H or C.sub.1 -C.sub.8 alkyl, preferably methyl; X.sup.5 is halo,
O--R.sup.9, or OCH.sub.3 OCO--R.sup.9 wherein R.sup.9 is selected
from any of C.sub.1 -C.sub.8 alkyl, C.sub.1 -C.sub.8 haloalkyl or
aryl, preferably X.sup.5 is chloro.
B.sup.2 may also be: ##STR16## wherein R.sup.10 is selected from
any of C.sub.1 -C.sub.8 alkyl or aryl, preferably methyl; X.sup.6
is halo, preferably chloro.
Alternatively, the A, B and S groups in an AB monomer may be
represented by the formula A.sup.3 (S.sup.2)B.sup.3 wherein:
A.sup.3 is selected from any of ##STR17## and B.sup.3 is selected
from any of ##STR18## wherein S.sup.2 is C.sub.1 -C.sub.8 alkyl,
aryl, substituted aralkyl or --(CH.sub.2 --CH.sub.2 --O--).sub.r,
wherein r is 1-12.
Alternatively, the AB monomer is a halo-alkylsubstituted styrene of
the formulas: ##STR19## wherein X.sup.6 is chlorine or bromine and
R.sup.11 is H or C.sub.1 -C.sub.6 alkyl. Preferably R.sup.11 is H
or CH.sub.3.
Currently preferred AB monomers may be selected from any of
1-(2-vinyloxyethyloxy)-1'-[2-(1-acetoxyethoxy)-ethyloxy]-4,4'-iso
propylidene diphenol;
1-vinyloxymethyl-4-(1-acetoxy)ethyloxymethylcyclohexane;
1-(2-vinyloxyethyl)-4-[1-acetoxyethyloxy)ethyl]terephthalate;2-(2-vinyloxy
ethyl)-2-[(1-acetoxyethyloxy)ethyl]diethyl malonate;
1-(2-vinyloxyethyl)-3-[(1-acetoxyethyloxy)ethyl]-5-(2-methacryloyoxyethyl)
-1,3,5-benzenetricarboxylate;
1-[(4-ethenyl)phenoxymethyl]-4-[4-(1-chloroethyl)phenoxymethyl]benzene;
4-(2-(1-chloroethyloxy))ethyloxystyrene; 4-(1-bromoethyl)styrene;
and 4-(1-chloroethyl)styrene and chloromethylstyrene.
As used herein, unless otherwise noted alkyl and alkoxy whether
used alone or as part of a substituent group, include straight and
branched chains. For example, alkyl radicals include methyl, ethyl,
propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-pentyl,
3-(2-methyl)butyl, 2-pentyl, 2-methylbutyl, neopentyl, n-hexyl,
2-hexyl and 2-methylpentyl. Alkoxy radicals are oxygen ethers
formed from the previously described straight or branched chain
alkyl groups.
The term "aryl" as used herein alone or in combination with other
terms indicates aromatic hydrocarbon groups such as phenyl or
naphthyl. The term "aralkyl" means an alkyl group substituted with
an aryl group.
While certain currently preferred substituents are identified
above, these are not intended in any manner to limit the
substituents which may be present on the various AB and C
compounds, provided that they do not interfere in the primary
polymerization reactions.
EXAMPLES
In the Examples, the following abbreviations have the meanings
recited: DMSO=Dimethyl sulfoxide; THF=Tetrahydrofuran;
CEVE=2-Chloroethyl vinyl ether; TLC=Thin layer chromatography;
Et=ethyl and SEC=Size-exclusion chromatography; Bu=butyl;
Ac=acetyl.
Example I
Preparation of Vinyl Ether-Type A-B Molecule (1)
1-(2-vinyloxyethyloxy)-1'-[2-(1-acetoxyethoxy)-ethyloxy]-4,4'-isopropyllid
enediphenol ##STR20##
A mixture of bisphenol A (23 g), powdered NaOH (12 g), and DMSO (45
ml) were heated at 70.degree.-75.degree. C. with stirring under
nitrogen for 1.5 hours. To the mixture, CEVE (39 g) was added
slowly over 2 hours. An additional 20 ml of DMSO was added to this
viscous mixture. Then the solution was heated for another 5 hours
at 70.degree.-75.degree. C., and was allowed to stand overnight at
room temperature. The reaction mixture was washed with water, and
the isolated crude product was purified by crystallizing twice from
ethanol. The aromatic bisvinyl ether (2) was obtained as a
white-pale yellow solid in 75% yield. The preparation of acetic
acid-adduct of aromatic bisvinyl ether was carried out as follows.
To the solution of aromatic bisvinyl ether 2 (7.4 g) in toluene (15
ml), was added a slight excess of glacial acetic acid (1.4 g). The
mixture was heated at 70.degree. C under nitrogen for 8 hours.
After cooling the mixture was evaporated to remove toluene and
unreacted acetic acid. A yellowish oil was obtained almost
quantitatively (>95%). TLC showed that the crude products
contained three major materials: unreacted 2, mono-adduct of acetic
acid to 2 vinyl ether 1, and di-adduct of acetic acid. The
mono-adduct of acetic acid to 2 (1), an A-B type molecule, was
separated from the mixture by flash chromatography eluting with
hexane/diethyl ether (60/40); the Rf values of three fractions are
0.56, 0.31, 0.14, respectively. The eluent was then removed on a
rotary evaporator and vacuum dried for 1 hour. A colorless
transparent oil was obtained (43% yield based on 2).
Cationic Polymerization of 1 as an A-B Type Molecule
Purified 1 was dissolved in dry THF and the solution was allowed to
stand overnight over granular CaH.sub.2, to remove trace amounts of
water. The transparent supernatant fraction was then transferred to
the reaction vessel and used to prepare the monomer solution.
Polymerization was carried out under dry nitrogen in a baked glass
vessel equipped with a three-way stopcock. The reaction was
initiated by addition of Et.sub.1.5 AlCl.sub.1.5 in toluene used as
an activator to the monomer solution in THF at 0.degree. C.
([Et.sub.1.5 AlCl.sub.1.5 ]0=[1].sub.0 =0.15 mol/l, total scale of
the reaction: 5 ml). THF was used as a solvent to stabilize the
propagating carbocations by its nucleophilic interaction and
prevent the occurrence of various side reactions such as
crosslinking, chain transfer reaction etc. After 24 hours, the
reaction was quenched by 2 ml of 0.3 wt % ammonia in methanol. The
quenched reaction mixture was diluted with ethyl acetate and then
washed with dilute hydrochloric acid (0.6 mol/l ) and water to
remove the initiator residues. After neutralization, the polymer
product was recovered by evaporation of the solvents under reduced
pressure, and vacuum dried overnight. The colorless polymer is
isolated quantitatively as a thicks liquid. The polymer is
completely soluble in THF, ethyl acetate, and chloroform. The
weight average molecular weight measured by SEC with polystyrene
standard (THF, 40.degree. C.) was MW=10.sup.4. The molecular weight
distribution curve showed a significant shoulder extending to
10.sup.5. The structure of the polymer was confirmed by NMR and
IR.
Example II
Preparation of Hyperbranched Poly (1) with Higher Molecular
Weight
The polymerization of 1 was carried out as above with addition of a
small amount of 2 (A-A type molecule, 0.01 mol/l ) after 24 hours
followed by quenching. The work up process was similar to that of
Example I. The polymer was obtained in 90% yield. The polymer is
completely soluble in THF, ethyl acetate, chloroform. The SEC of
the polymer shows a value of MW=3.times.10.sup.5.
Example III
Preparation of Vinyl Ether-Type A-B Molecule (3)
1-vinyloxymethyl-4-(1-acetoxy)ethyloxymethylcyclohexane
##STR21##
Vinyl ether-type A-B molecule 3 was prepared by the following two
steps that include the synthesis of bisvinyl ether 4 by vinyl
transetherification and the reaction with acetic acid. To a
solution of distilled ethyl vinyl ether (29 ml, 0.3 mol),
1,4-cyclohexyldimethanol (11 g, 0.075 mol), and 1,4-dioxane (15 ml)
were added mercury (II) acetate (0.75 g, 0.0024 mol) as a catalyst
and molecular sieves 4A (20 g) as an adsorbent of ethanol. The
reaction was carried out at room temperature for 5 hours with
occasional shaking. The reaction was then stopped by adding 2 g of
anhydrous potassium carbonate. The reaction mixture was washed with
water, dried over Na.sub.2 SO.sub.4, and fractionated by flash
chromatography eluting with hexane/diethyl ether (50/50) (yield
.about.20%).
The reaction of 4 (5.2 g) with acetic acid (1.9 g) was carried out
at 70.degree. C. under nitrogen. After 4 hours, the reaction
mixture was allowed to cool, and evaporated to remove unreacted
acetic acid. A colorless oil was obtained. The mono-adduct of
acetic acid to 4, an A-B type molecule (3), was separated from the
mixture by flash chromatography eluting with hexane/diethyl ether
(80/20). The eluent was removed on a rotary evaporator and vacuum
dried for 1 hour. The product was obtained as a colorless
transparent oil (40% yield based on 4).
Cationic Polymerization of 3 as an A-B Type Molecule
Purified 3 was dissolved in dry ethyl acetate and the solution was
allowed to stand overnight over granular CaH.sub.2 to remove trace
amounts of water. The transparent supernatant fraction was
transferred to the reaction vessel and used to prepare the monomer
solution. The polymerization process was similar to that of
compound 1 (see Example I) except for the use of EtAlCl.sub.2 as
the activator instead of Et.sub.1.5 AlCl.sub.1.5. The reaction was
initiated by addition of EtAlCl.sub.2 in hexanes to a monomer
solution in ethyl acetate at 0.degree. C. ([EtAlCl.sub.2 ].sub.0
=[3].sub.0 =0.15 mol/l, total scale of the reaction: 5 ml). Ethyl
acetate was used as a solvent to stabilize the propagating
carbocations by its nucleophilic interaction and prevent the
occurrence of various side reactions such as crosslinking, chain
transfer reaction etc. The polymerization reaction progressed
homogeneously. After 2 hours, the reaction was quenched by 2 ml of
0.3 wt % ammonia in methanol. Work up was as described for compound
1 (see Example I). The polymer was obtained in 97% yield as a
viscous liquid. The polymer was completely soluble in THF, ethyl
acetate, chloroform. The weight average molecular weight measured
by SEC with polystyrene standard (THF, 40.degree. C.) was
MW=15,000. The molecular weight distribution curve showed a
shoulder extending above 10.sup.5. The structure of the polymers
was confirmed by NMR and IR.
Example IV
Preparation of Vinyl Ether-Type A-B Molecule (5)
1-(2-vinyloxyethyl)-4-[1-acetoxyethyloxy)ethyl]terephthalate
A solution of terephthaloyl chloride (10 g, 0.05 mol) in diethyl
ether (60 ml) was added slowly to the solution of 2-hydroxyethyl
vinyl ether (11 g, 0.12 mol) in pyridine (17 g) at 0.degree. C.
with stirring under nitrogen. The reaction mixture was allowed to
react for another 15 min at 0.degree. C., and then left overnight
at room temperature ##STR22## with stirring under nitrogen. The
solution was poured into water (300 ml) with stirring, and the
product was extracted with diethyl ether. The organic layer was
washed with water, and dried over MgSO.sub.4. The product was
recovered by evaporation of the solvent under reduced pressure, to
yield a white solid (15 g, 96% based on terephthaloyl chloride).
The compound was purified by flash chromatography eluting with
CH.sub.2 Cl.sub.2 to give 12 g of compound 6. The preparation of
the acetic acid-adduct was carried out as previously described for
compound 1 (see Example I). To the solution of 6 (5 g) in toluene
(14 ml), was added a slight excess of glacial acetic acid (1.2 g),
and the mixture was heated at 70.degree. C. under nitrogen for 10
hours. The reaction mixture was then allowed to cool and evaporated
to remove toluene and unreacted acetic acid. The colorless oil was
obtained almost quantitatively (>95%).
The mono-adduct of acetic acid to 6, an A-B type molecule 5, was
separated from the mixture by flash chromatography eluting with
hexane/diethyl ether (50/50). The eluent was then removed on a
rotary evaporator and vacuum dried for 1 hour. A white solid was
obtained (41% yield based on terephthaloyl chloride).
Cationic Polymerization of 5 as an A-B Type Molecule
Purified 5 was dissolved in dry THF and allowed to stand overnight
over granular CaH.sub.2 to remove trace amounts of water. The
polymerization and following work up processes were similar to
those for compound 3 (Example III). The polymer was obtained in 95%
yield. The polymer was completely soluble in THF, ethyl acetate,
chloroform. The polymer was characterized as described in Examples
I and III.
Example V
Preparation of Vinyl Ether-Type A-B Molecule (7)
2-(2-vinyloxyethyl)-2-[(1-acetoxyethyloxy)ethyl]diethyl malonate
##STR23##
To a solution of sodium ethoxide (8.7 g) in absolute ethanol (71
ml) was added at room temperature, ethyl malonate (19 g) and CEVE
(24 ml) in this order. The solution was heated at reflux with
stirring under nitrogen for 5 hours. After most of the ethanol was
evaporated under reduced pressure, the reaction mixture was diluted
with diethyl ether, and the sodium chloride was filtered off. The
organic layer was washed with 10% aqueous NaCl, then dried over
MgSO.sub.4, and evaporated under reduced pressure to give a liquid
product in almost quantitative yield.
Compound 9 was prepared by the reaction of CEVE (10 g) and a slight
excess of glacial acetic acid (7 g) at 40.degree. C. under nitrogen
overnight, to give a slightly yellowish liquid almost
quantitatively. Quantitative addition of acetic acid was also
confirmed by 1H NMR. The solution of sodium salt of 8 was prepared
by treating distilled 8 with sodium hydride in THF at 40.degree. C.
under nitrogen for 1 hour. The reaction with excess distilled
compound 9 was carried out at 40.degree. C. under nitrogen for 24
hours. The resulting reaction mixture was washed with water, dried
with MgSO.sub.4, and then evaporated. The crude product was
purified by chromatography, to give compound 7 in 48% yield.
Cationic Polymerization of 7 as an A-B Type Molecule
Purified 7 was dissolved in dry THF and the solution was allowed to
stand overnight over granular CaH.sub.2 just before use as a
monomer solution, to remove trace amounts of water. The
polymerization and the following work up process were similar to
those for compound 3 (see Example III). The polymer was obtained in
a 95% yield. The polymer was completely soluble in THF, ethyl
acetate, and chloroform. The polymer was characterized as described
in Examples I and III.
Example VI
Preparation of Vinyl Ether-Type with a Functional group (10)
1(2-vinyloxyethyl)-3-[(1-acetoxyethyloxy)ethyl]-5-(2-methacryloyloxyethyl)
-1,3,5-benzene tricarboxylate ##STR24##
A solution of 1,3,5-benzenetricarbonyl trichloride (1.8 g),
purified by recrystallization from hexanes, in CH.sub.2 Cl.sub.2
(20 ml) was slowly added to the solution of 2-hydroxyethyl vinyl
ether (1.2 g) and 2-hydroxyethyl methacrylate (0.8 g) in pyridine
(60 ml) at 0.degree. C. with stirring under nitrogen, and the
mixture was allowed to stir overnight at room temperature. The
solution was diluted with CH.sub.2 Cl.sub.2, washed with water, and
dried over MgSO4, and the solvent was removed under reduced
pressure. The compound having two vinyloxy groups and one
methacrylate group 11 was separated by flash chromatography eluting
with hexane/diethyl ether to give compound 11 (35% based on
1,3,5-benzenetricarbonyl trichloride).
The preparation of the acetic acid-adduct was carried out in a
manner similar to that for compound 1 (see Example I). To the
solution of 11 (3.2 g) in toluene (14 ml), was added a slight
excess of glacial acetic acid (0.6 g), and the mixture was heated
at 70.degree. C. under nitrogen for 10 hours. The reaction mixture
was then allowed to cool and evaporated to remove toluene and
unreacted acetic acid. The colorless oil was obtained almost
quantitatively (>95%).
The mono-adduct of acetic acid to 11, an AB-type molecule having a
pendant functional group (10), was separated from the mixture by
chromatography. The eluent was then removed on a rotary evaporator
and vacuum dried for 1 hour. A white solid was obtained (41% based
on 11).
Cationic Polymerization of 10 as an A-B Type Molecule
Purified 10 was dissolved in dry THF and the solution was allowed
to stand overnight over granular CaH.sub.2 to remove trace amounts
of water. The polymerization and the following work up process were
similar to that for compound 3 (see Example III). The polymer was
obtained in 95% yield. The polymer was completely soluble in THF,
ethyl acetate, and chloroform. The polymer was characterized as
described in Examples I and III.
Example VII
Preparation of Styrene-Type A-B Molecule (12)
1-[(4-ethenyl)phenoxymethyl]-4-[4]-(1-chloroethyl)phenoxymethyl]benzene
##STR25##
A mixture of freshly prepared p-hydroxystyrene (12 g),
.alpha.,.alpha.'-di-bromo-p-xylene (13.2 g), dried potassium
carbonate (17.3 g), and 18-crown-6 (2.6 g) in dry acetone (100 ml)
was heated to reflux and stirred vigorously under nitrogen for 20
hours. The reaction mixture was allowed to cool and evaporated to
dryness. The residue was partitioned between CH.sub.2 Cl.sub.2 and
water, and the aqueous layer was further extracted with CH.sub.2
Cl.sub.2. The combined organic layers were then dried and
evaporated to dryness. After purification by chromatography a 26%
yield of compound 13 was isolated.
The HCl-adduct was prepared by bubbling dry HCl gas through a
solution of 13 in toluene at 0.degree. C. The formation of
mono-adduct of HCl 12 was followed by TLC, which showed that the
crude product contained four materials. Any remaining HCl in the
solution was removed by bubbling dry nitrogen gas. The mono-adduct
of HCl to 13 (12), an A-B type molecule, was separated from the
mixture by chromatography. After evaporation of the solvent under
reduced pressure and vacuum drying, 12 was obtained in 31%
yield.
Cationic Polymerization of 12 as an A-B Type Molecule
Purified 12 was dissolved in dry toluene. The polymerization
process was similar to that of compound 1 (Example I), except for
the use of different activator. Polymerization was carried out
under dry nitrogen in a baked glass vessel equipped with a
three-way stopcock. The reaction was initiated by mixing the of
ZnCl.sub.2 in diethyl ether to the monomer solution in toluene at
0.degree. C. ([12].sub.0 =0.15 mol/l, [ZnCl.sub.2 ].sub.0 =0.03
mol/l, total scale of the reaction: 5 ml). The work up process was
also similar to that of compound 1 (Example I). The polymer was
obtained in 85% yield. The polymer was completely soluble in THF,
ethyl acetate, and chloroform. The polymer was characterized as
described in Examples I and III.
Example VIII
Preparation of Styrene-Type A-B Molecule (14) 4-(2-(1-chloroethyl
oxy))ethyloxystyrene ##STR26##
A mixture of p-hydroxystryrene (12 g), powdered NaOH (6 g),and DMSO
(40 ml) was heated at 70.degree.-75.degree. C. with stirring under
nitrogen for 1.5 hours. To the mixture, CEVE (20 g) was added
slowly over 2 hours. Then the solution was heated for another 5
hours at 70.degree.-75.degree. C., and was allowed to stand
overnight at room temperature. The reaction mixture was washed with
water, and the isolated crude products were purified by
crystallization. Compound 15 was obtained in 70% yield. The
HCl-adduct to 15 was prepared by bubbling dry HCl gas through a
solution of 15 in toluene at 0.degree. C. The formation of
mono-adduct of HCl (14) was followed by TLC. Any remaining HCl in
the solution was removed by bubbling dry nitrogen gas. The
mono-adduct of HCl to 15, an A-B type molecule, was separated from
the mixture by chromatography. After evaporation of the solvent
under reduced pressure and vacuum drying, 14 was obtained in 46%
yield.
Cationic Polymerization of 14 as an A-B Type Molecule
Purified 14 was dissolved in dry toluene. The polymerization
process was same as that of compound 12 (Example VII). The reaction
was initiated by mixing the ZnCl.sub.2 in diethyl ether used as an
activator and the monomer solution in toluene at 0.degree. C.
([14].sub.0 =0.15 mol/l, [ZnCl.sub.2 ].sub.0 =0.06 mol/l, total
scale of the reaction: 5 ml). The work up process was also the same
as that for compound 12 (see Example VII). A viscous polymer was
obtained in 80% yield. The polymer was completely soluble in THF,
ethyl acetate, chloroform. The polymer was characterized as
described in Examples I and III.
Example IX
Copolymerization of Two Different A-B Type Molecules
The copolymerization of two different A-B type molecules of
comparable reactivities was carried out similarly to Examples I and
III. Purified 1 and 3 were dissolved in dry THF and the solution
was allowed to stand overnight over granular CaH.sub.2 to remove
trace amounts of water. The transparent supernatant fraction was
transferred to the reaction vessel and used as the monomer
solution. The polymerization process was similar to those for
compound 3 (see Example III). The reaction was initiated by
addition of EtAlCl.sub.2 in hexanes to a monomer solution in THF at
0.degree. C. ([EtAlCl.sub.2 ].sub.0 =[1].sub.0 +[3].sub.0 =0.15
mol/l, total scale of the reaction: 5 ml). THF was used as a
solvent to stabilize the propagating carbocations by its
nucleophilic interaction and prevent the occurrence of various side
reactions such as crosslinking, chain transfer reaction etc. After
10 hours, the reaction was quenched by 2 ml of 0.3 wt % ammonia in
methanol. Work up was as described for compound 1 (see Example I).
The polymer was obtained in 97% yield as a viscous liquid. The
polymer was completely soluble in THF, ethyl acetate, chloroform.
The polymer was characterized as described in Examples I and
III.
Example X
Polymerization of 4-(1-chloroethyl)styrene.
A freshly dried glass apparatus was used for this polymerization
under nitrogen atmosphere. A solution of 4-(1-chloroethyl)styrene
(0.55 g, 3.3 mmoles) in dichloromethane (4.5 ml) was cooled to
0.degree. C. then pre-cooled SnCl.sub.4 (0.5 ml of 1M solution in
dichloromethane) was added under nitrogen. A color-change was
observed upon mixing and after 8 hours the polymerization was
quenched by addition of pre-chilled methanol (2 ml) containing a
trace of ammonia. The color was discharged and the mixture diluted
with dichloromethane (30 ml) then washed with 2% aqueous HCl, (40
ml) and distilled water (5 times, 40 ml each). The organic layer
was concentrated and the polymer (80% yield) isolated by
precipitation. The polymer was soluble in THF. After
reprecipitation into hexane its molecular weight measured by
standard GPC with polystyrene standards was approximately 90,000
daltons while the molecular weight obtained by universal
calibration using in-line viscometry was 300,000 daltons,
confirming the hyperbranched character of the product. The
structure of the polymer was further confirmed by NMR in CDCl.sub.3
and by infrared analysis.
Example XI
Polymerization of 4-(1-chloroethyl)styrene.
The polymerization of the same monomer was also accomplished as
described above using inverse addition of the pre-chilled monomer
solution (4 mmoles) in dichloromethane (5 ml) to a solution
containing SnCl.sub.4 (2 mmoles) and tetrabutylammonium chloride (1
mmole) in dichloromethane cooled to -30.degree. C. Once the
addition was complete the mixture was brought slowly from
-30.degree. C. to 0.degree. C. with occasional mixing until the
polymerization was quenched after 12 hours as described above. The
polymer was processed and characterized as described above in
Example X.
* * * * *